It’s typically not an instant thing. Below is the description from page 25 of the pdf linked by OP, from which the charts were taken; I have highlighted some mentioned timeframes. There is also a graph on page 24 showing the change over time.
India’s process of autocratization begins in earnest from 2008 and characteristically proceeded in the incremental, slow-moving fashion of the “third wave”. Over the years, India’s autocratization process has been well documented, including gradual but substantial deterioration of freedom of expression, compromising independence of the media, crackdowns on social media, harassments of journalists critical of the government, as well as attacks on civil society and intimidation of the opposition. The ruling anti-pluralist, Hindu-nationalist Bharatiya Janata Party (BJP) with Prime Minister Modi at the helm has for example used laws on sedition, defamation, and counterterrorism to silence critics. The BJP government undermined the constitution’s commitment to secularism by amending the Unlawful Activities (Prevention) Act (UAPA) in 2019. The Modi-led government also continues to suppress the freedom of religion rights. Intimidation of political opponents and people protesting government policies, as well as silencing of dissent in academia are now prevalent. India dropped down to electoral autocracy in 2018 and remains in this category by the end of 2023.
The report provides sources, as well as its criteria and methodology. If you are interested in facts, you may find them there.